Sharply rising prices have triggered food riots in recent weeks in Mexico, Morocco, Senegal, Uzbekistan, Guinea, Mauritania and Yemen, and aid agencies around the world worry they may be unable to feed the poorest of the poor.

In the Philippines, officials are raiding warehouses in Manila looking for unscrupulous traders hoarding rice, while in South Korea, panicked housewives recently stripped grocery-store shelves of food when the cost of ramen, an instant noodle made from wheat, suddenly rose.

The shadow of “a new hunger” that has made food too expensive for millions is the result of a sudden and dramatic surge in food prices around the world.

Rising prices for all the world’s crucial cereal crops and growing fears of scarcity are careening through international markets, creating turmoil.

Last Thursday, as world rice prices soared by as much as 30% in one day, Egypt decided to suspend rice exports for six months to meet domestic demand and to try to limit price increases.